Monday, September 18, 2006

Stooping to conquer: How to become multicellular

Stooping to conquer: How to become multicellular, The Economist, August 10, 2006 ...

[Graphic: A Volvox carteri colony, University of Arizona]

VIEWED from humanity's lofty heights, single-celled creatures are the scum of the earth. In reality, though, almost all living things are unicellular, and with good reason. Multicellularity requires most of the cells in a body to make the supreme Darwinian sacrifice, by giving up reproducing. This helps the few cells specialised for reproduction to do so more effectively. Since the self-sacrificing cells have the same genes as the specialised reproducers they are, in effect, reproducing collaterally. But it is still a hard trick to pull off, and it has not happened often. This shows again the unfalsifiability of selfish-gene Darwinism. When it is contradicted by "cells ... giving up reproducing," it is spin-doctored into "cells ...make the supreme Darwinian sacrifice, by giving up reproducing!

One creature that has managed the trick-separately from plants, animals and fungi, who are the real experts in the field-is an alga called Volvox carteri. An adult Volvox consists of around 2,000 body cells, whose job is to move the organism around using their flagella, and 16 cells capable of reproducing. ... Darwinists cite Volvox as an example of how multicellularity arose. Thus Richard Dawkins writes of Volvox "... it is possible that they represent the kind of thing that went on more than a thousand million years ago, when our kind of cells first started to band together into colonies" (his emphasis):

"The eucaryotic cell is now seen as derived from a colony of bacteria. Eucaryotic cells themselves later got together into colonies. Volvox are modern creatures. But it is possible that they represent the kind of thing that went on more than a thousand million years ago, when our kind of cells first started to band together into colonies. This ganging up of eucaryotic cells was comparable to the earlier ganging up of bacteria into eucaryotic cells and the even earlier ganging up of genes into bacteria." (Dawkins R., "Climbing Mount Improbable," Penguin: London, 1996, pp.263-264. Reference omitted. Emphasis original)

Note Dawkins' "Volvox are modern creatures." Presumably he was (perhaps unconsciously) trying to anticipate the next question: if "Natural selection" is a "blind, unconscious, automatic process" (my emphasis):

"Natural selection, the blind, unconscious, automatic process which Darwin discovered, and which we now know is the explanation for the existence and apparently purposeful form of all life, has no purpose in mind. It has no mind and no mind's eye. It does not plan for the future. It has no vision, no foresight, no sight at all. If it can be said to play the role of watchmaker in nature, it is the blind watchmaker." (Dawkins, R., "The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design," W.W Norton & Co: New York NY, 1986, p.5)

and Volvox (i.e. their order Volvocales) have existed for "more than a thousand million years" (which I assume is in fact the case) then why has Volvox never taken the next step to true multicellularity, if it is advantageous? If it is not advantageous, then an explanation would be needed for why other Volvox-like eukaryotic colonies (or colony) did take the next step to multicellularity (which, since I accept common ancestry, I assume did in fact happen).

But if Dawkins' "Volvox are modern creatures" was an attempt to cover himself for the above question, it won't work. Living cyanobacteria are also "modern creatures" (as are living anything) but that does not change the fact that they originated at least ~3.5 billion years ago and have remained essentially unchanged ever since.

The answer to the question cannot be lack of random mutations, since there must have been uncountable googolplexillions of random mutations in the presumed billions of years that Volvox has existed. And likewise, the answer cannot be lack of environmental change in that vast length of time.

Finally, "resisted change and have survived in the ecological niche":

"From the emergence of the eucaryotes between 1.4 and 1.2 billion years ago onward, they began to advance the efficiency of their revolutionary new cellular organization. ... Around this time some eucaryotic cells began to forsake their solitary ways and began to share a colony as a loosely associated collection of individuals. In a comparatively short time the colony took on a character of its own as the individual cells became more dependent on being a part of it. The cells interacted with each other by excreting chemicals and ions which affected the biochemical synthesis governing reproduction and products in each other. In this way cells within the colony became specialized and different from each other in the group. The colonies that were most successful with this group-living in the gathering of nutrients and protection against predation evolved and passed on the genetic propensity for differentiation necessary for colonial organization. The scenario is not purely conjectural. There are found today living systems in this intermediate stage of organization in which cells become colonies, united and specialized, but not to the extent that they may be classified as multicellular organisms. Among the green algae there is a one-cellular form which has a chloroplast, an eyespot, and two flagella, or threadlike projections, used for locomotion and the movement of water currents. Within this family are the Pandorina, some of whom form colonies of four to thirty-two cells. These colonies are not merely aggregates, because the cells swim by coordinated movement of their flagella. The Gonium is another member of this group that forms colonies. But the most evolved colony formation is carried on by the Volvox. This genus of pale green flagellates forms a colony of 500 to 50,000 cells arranged in a hollow sphere about one-fiftieth of an inch in diameter. Whereas the cells of the Pandorina and Gonium look alike, the cells of the Volvox become specialized; the cells at the front of the ball have larger eyespots, and only some of the cells reproduce themselves. Thin strands of protoplasm connect the cells to one another in the colony. The colony is reproduced when cells in the back begin to divide, producing a new small ball of cells that is released to the inside of the parent colony. When the old colony dies, the young colonies inside are released to disperse and repeat the cycle. From colony formation the eucaryotes were crossing the threshold to become Metazoa, or multicellular animals. As there are of most stages of evolutionary development, there are living species which have resisted change and have survived in the ecological niche that was prevalent at the time that level of development was widespread." (Day, W., "Genesis on Planet Earth: The Search for Life's Beginning," [1979], Yale University Press: New Haven CT, Second Edition, 1984, pp.32-33)

is just a restatement of the problem, not its solution!

So once again, the Darwinian `blind watchmaker' mechanism: the natural selection of random micromutations, may be an adequate explanation of some small-scale change (aka. "microevolution"), but it fails as an explanation of large-scale biological change (aka. "macroevolution"), in this case the origin of multicellularity.

Stephen E. Jones, BSc (Biol).
Genesis 2:7. the LORD God formed the man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being.